UNCLASSIFIED - Defense Technical Information .UNCLASSIFIED AD;2517789. ARMED SERVICES TECHNICAL U*IO]M

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  • UNCLASSIFIED

    AD;2571 789.

    ARMED SERVICES TECHNICAL U*IO]M ATKMARLIWO HALL ST1WARIMK 12, V11011

    UNCLASSIFIEDBest Available Copy

  • NOTICE: ;&- governwut or ether drawings, speci-fications or other data are used for sny pmrposeother t1a in connection vith a definitely relatedgurernnt procurent operation, the U. S.Govem t thereby Incurs no responsibility, nor anyobli.,oz vhat-oever; and the feat that the Goven-=ert my hwme fomlated, frmished, ur in any vaysupplied the said d--Arngs, specifications, or otherdata is nit to be regarded by icp.lcation or other-vise as in any naer licensing the ho3 A or anyother Person or corporation, or conveying any rigitsor permission to =r2efae-re, use or sell anyptented Inv,-tiom that my in any vay be relatedthereto.

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    130Techniclco Report-----~ WATER VAPOR TRANSMISSION OF

    .......... PLAIN CONCRETE

    C- 16 May 1%I

    .. . . . .LLJ~

    .F4.

    U.S.NVL..ILEGIERIGLAOATR

    Pbr Hueeme Caior

    UZA

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    WATER VAPOR TRANSMISSION OF PLAIN CONCRETE

    Y-RM1 1-01-025

    Type C

    by

    D. F. Griffin, R. L. Henry

    OBJECT OF TASK

    To measure water vapor permeability of concrete and relate it to corrosion ofembedded steel; to investigate sa!t whisker crystal growth on cocreMte; and to meas-ure electriial resistivity of concrete.

    III

    ABSTRACTI

    The effects of water-cement ratio, relative h."n idity, aggregate size, concreteslsee positi,, and ccrtain admixturmS such as oleic acid and sodium chloride on thepermeability of plain concrete were investigated. lcluded is a qtorter replicatestatistical experiment for two levels of each of six factors to permit an analysis ofvariawce of different variables in the permeability study. Salt whisker crystal growthon specimens with sodium chloride as an admixture, believed to be reported for thefirst time, is discussed.

    Water vapor ir ion values were found to be significantly higher forhither water-cement ratios, .maller oggega~e, and the absence of sodium chloride.Concrete slice position, oleic =cid, and relative humidity were found to have nosignficant effect when compvred w-ith eqerimental variability.

    The study demonsmTates that water vapor transmission is not directly proportionalto -water a-pressum differentials between the ends of the flow path.

    The investigation of water vapor transmission in plain coi.-.crete will continue,together with studies of the electrical restivity of concrete and the relation of watervapor transmission to the corrosion of steel in reinforced concrete.

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    CONTENTSpage

    BACKGROUND .............................. 1

    SSTATEMENT OF THE PROBME. ...................... 4

    APPROACH TO THE PROBLEM ...................... 4

    RESEARCH PROGRAM .......................... 4

    Phasel . ..... .......... ...... ...... .......... 4

    Discuss7io of Phase I (Results) ... .... .......... .... .... 14

    Phase if ..................... 0........ . 21

    D.scussion of Phase 11 (Results) .................... 23

    Comparison of Phase I cnd Phase II ........... * ...... 26

    Sodium Chloride Study ........................ 29

    Sodim Chloride Whisker Crystals .......... .. *. .. .. 33

    FINDINGS . .. ............................ *. 36

    CONCLUSIONS ............................. .3

    FUTURE PLANS ................. ...... ... 37

    ACWNOWLEDGMENT .......................... 37

    REFERENCES ... . ............. ................ 38

    APPENDIXES'

    A - PLASTIC WET CUP DESCRIPTION ................. 39

    B - WET CUP ASSEMBLY ................................. 40,

    C - ANALYSIS OF VARIANCE ..................... 42

    DISTRIBUi ON LIST .............. o ............ 45

    LISARY. CATALOG CARD .......... o .............

    "St'iN - [Na!! i!,- ,,

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    IFiguu I. Galvanized steel wet cup and manometer.

    a.

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  • InI -rowith a fil .- d of renocc cl o.t stiN tu [IN inJ dII

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    t- BA KGl~flL:-'O

    S~~in ". :tion with a *illi v~udy of reinforced coral concrete structures inStropical ::-.. conducted b"y Pro.fe_sr C. s. $cho!e =-nder Contract NBy-3171 of Ir ]~5 Marc: 59,t en in conf-,'ctk.n -with Task Y-RO07-05-( i2-. core sonples were

    Sdrilled frr these struc!~,.res in ord.r to determine their water v)or permeability.SThe wet- -.-- method v: !-ee'eJ most suitable for this psrps.

    Twenty-six sanples, approximately 3.5 inches in diameter and 1.5 inchesthick, were sealed in galvanized steel cups by using alternating layevs of plasteraf Paris and 3M secler (EC879), as sho in the cron sctrio. of a cup in figre 1.

    A few days afttr ie;rng placed in a 2D-p-.tc;--r riy ivr a-ldiy room at73.4 F. several of the specimens showed a z.--" vh -=- ts. surface(Fi=e 7j. An X--ruy iifrctrion analys:s rxvecied thi- Qti-.j% . e pimarilysodiurm chloride. A setniquatitctive Vec trogaphic m-uty-sim L-i-uc-.4 the principalcation to be No; traces of Ca, Al, Mg, Si, Fe, and Cu wrere i tected.

    thc. wa: no direct conraction between the c-Spaent qiantity of salt whiskergrowth r.id the amount of salt present in the concrete. A cia--nica; - -alysis of thecrex , tv - that all chl-wides expes',e4 as a p-ercentage of N.-!- by weig.htof osue ronged from 0.1,6 to 1.95. Vigorous -qaisker grow4h as well as traces

    of gi..r WAf wwe Observed oni Sjscimens to-t!nirdne higk. C* W--* as 'low salt, k.q'icatinfi that oil- for. s Lnflve.ncin-s ,i'sker gir._w wth ,.e present.

    The quantitativ v ar. pea-oility were incon.clusive because over aperiod of time many a f sov-- imens ware di-l.6dged in the cups by internal pressuresfF'i~re 3). To . .eg -is pher.ommeron, a mercury manometer was placed on an

    n.-stu pcd -p t os ,-- Fire 1. it behaved in a repeatable manner, duringthmt fPast -- .--4 cyzcury vacuum pressure developed and during the follow-ing six w-,.e- c pv- ire of up to 74 -- " e",,-." ;oped. It wasconcluded '-- . invers.iotors tf.-Ai sch pressures cojld . a specimen fromits seal.

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  • Figure- 2. So iu ch ord wh s e

    J~go t n c r l con

    ret . ] .. ~i .--i ..

    ii

    glaie steel cu-cetem ... talt ic cope causin .am reeseomyda

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    Figurre 2. Sodium chlc~rde whisker crsal growth on cora concrete.

    A. moss spect-ometric analysis o' the gas in ,he cup indicated that .oporoximatety20 percent by volume wos hydoe; no nantccnos~he~ric gas was detected~. One- pos-sible explanation For tho presence of hydroge is that the zinc nd the iron in thegalvanized steel cup created an electrolytlc couple, causing a release of hy/drogen

    gas.

    T

    2

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    t

    Rgure 3. Effects of ntemol pressure coused by generction of Ihy&ooen gas ;n goivzed steel cup.

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  • STATEMENT OF THE PROBLEM

    As an outgrowth of the above study, it was desired to explore the subjectfurther. A literature search revealed tfvt very little information exists about water

    apor permeability of portland cement concrete. Therefore, a Laboratory SelectedResearch Task was established to determine whether or not significant relationshipsexist btween the spoiling and cracking of reinforced concrete, the effects of"mrlh, chloride incorporated in the concrete, electrical conductivity of concrete,cnd waohm vapor permeability of the concrete. The corrosion of reinforcing stet:sassociated with concrete strictures, spalling and cracking of concrete, and elec-trictal conductivity of concrete will be subjects of separate reports.

    APPROACH TO THE PROBLEM

    An inert material was needed to replace the steel cup; therefore, acrylicresin tubes and sheets were chosen as the most economical inert materials for fabri-cation of the wet cups.

    Concrete cylinders 4 inches in dimneter and 8 inches long were cast, fromwhich 1.5-inch-thick speci.-nens were cut. Thirty cylinders were cast from each2.25-cubic-foot batch of concrete mixed in a Lancaster mixer.

    Since the sealer used for previous specimens was inadequate, another materialhad to be found. A sealer was required that would (1) bond to the concrete as wellas the acrylic tube, (2) be inert, (3) be impervious to vapor t!,m.ission, and (4) beable to withstand unpredictable pressures inside the cups., Shell Epon Resin No. 815combined with Shell Epon Curing Agent T-1 was fo'-nd to meet the requLrements.

    RESEARCH PROGRAM

    Phase

    The first study, hereafter referred to as Phase 1, was = follows:

    1. The first factor in the experiment to be varled with respect to thepe'meability was strength of concrete - defined by water-cement ratio. All threeconcretes - high, mediiti, and low strengths - were designed for equial water

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    contents and a 3/4-inch maximum ogg~rete particle size. The strength was variedby varying the cement content and adjusting the proportions of fine and coarseaggregate. All concrese mixes were designed for equal consistencies without addi-tives or odnixtures; a 3-inch slump was used as the measure of consist!ncy. SeeTable I for the complete mix designs. The cylinders not cut for wet cups were restedfor compm.-sive strength after fourleen days of fog curing at 73.4 F to obtain basicinformation about the standard deviattons of compressive strengths.

    2. The second fator to b varied was the absence or presence of sodiumchloride as an admixture. The Gnount of NaCI to be added was 1.5 percent byweight of plastic concrete, based on the NaCI contert of the coral concrete samples.The NaCI was dissolved in the mixing water before the a,,.mt was cdded ,o the batch.

    3. The third factor to be varied was the anbient con1it&,n in vhl;-